In answer to the question, "What did you do on your summer vacation?", this is my answer. Part of it, anyway.

You're looking down into someone's cranium. The broad bony area covering the top half is, depending on how you want to look at it, either the floor upon which your brain's frontal lobes lie, or the roof over your eyes. Dividing this area, you'll notice, are two parallel grooves, separated by a narrow shark fin of bone. The fin is the crista galli. In life, each of those grooves contains one half of your olfactory tract. Curl your hands into fists, extend your index fingers, and bring your two hands side by side, so your index fingers extend beside each other, and you've got the basic layout. Your index fingers, of course, are lying in the grooves. Your fists are the two hemispheres of your brain.

Now, notice the tiny holes in the grooves. Nerve cells down in your nasal passages reach up through those holes to the nerve cells in your olfactory tracts, to pass messages that you're smelling something. These cells then distribute the message to other parts of your brain. These parts of your brain tell you what it is you're smelling, how strong the odour is, and how you feel about it. Mom's home cookin', or something less appealing?

The large semicircle at the bottom is where your spinal cord would exit/enter.